Bone plates for fracture treatment are typically fixed to bone substantially parallel to a longitudinal bone axis using screws or other fixation elements. The bone plates have to be firmly fixed to the bone to prevent bone fragments from moving relative to each other. When fixing a bone plate to bone particular care has to be taken in case of peri-implant fractures, including periprosthetic fractures, for example. Periprosthetic fractures are fractures around a joint prosthesis, whereas peri-implant fractures more generally denote fractures around an implant.
When a periprosthetic fracture is to be treated, wherein a prosthetic device (e.g., with a ball joint and a stem) partially extends into a medullary canal of the fractured bone, the surgeon generally has to keep in mind that the fixation elements must not intrude into the medullary canal where the prosthetic device has been inserted. In such cases, an attachment device can be used which is adapted to accommodate the bone plate.
U.S. Pat. No. 4,973,332 and U.S. Pat. Pub. No. 2010/0262194 each discloses periprosthetic repair systems comprising a femur plate and an attachment device. The femur plates shown are configured to hold fracture parts of the femur together to promote healing of the fractured bone, for example. The attachment devices are adapted to be arranged on the femur plates. Specifically, the attachment devices form a partial overlay which fits over and accommodates the femur plate.
The attachment devices known from U.S. Pat. No. 4,973,332 and U.S. Pat. Pub. No. 2010/0262194 include finger-like structures or wings that are inclined with respect to a central portion of the attachment devices and are adapted to extend around at least a portion of the femur. For anchoring the attachment devices in the femur, each wing has a hole for receiving a screw which is screwed into the femur.
When attaching the femur plate using the attachment device, it is desired that this attachment offers a high stability so that the bone fragments of the fractured femur can effectively consolidate. However, when a prosthetic device extends along the length of the femur, the screws for anchoring the attachment device are preferably anchored in the outer hard layer of the bone. That is, they preferably should not penetrate into the medullary canal of the femur.